Metallic circuit for multiple-switch board systems



(No Model.) 2 SheetsSheet 1.

J. A. SEELY.

' METALLIC 013cm? FOR MULTIPLE SWITOHBOARD SYSTEMS.

No. 491,252. Patented Feb. 7, 1893.

(No Model.)

J. A. SEELY.

2 Sheets-Sheet 2.

METALLIC? CIRCUIT PUB MULTIPLE SWITGHBOARD SYSTEMS.

Patented Feb. 7, 1898'.

hi a/ 2237".

wi y,

hairs States a'rnn r rricn,

JOHN A. SEELY, OF NElV YORK, N. Y., ASSIGNOR TO THE WESTERN ELECTRIC COMPANY, OF CHICAGO, ILLINOIS.

METALLIC ClRGUlT FOR MULTiPLE-SWITCHBOARD SYSTEMS.

$ZPECIFICATION forming part of Letters Patent No. 491,252, dated February 7, 1893.

Application filed November 15, 1886. Serial No. 218,947. (No model.)

To all who???) it may GO'ILOGPTL. Referring to Fig. 1, it will be seen that Be it known that I, JOHN A. SEELY, a citibranch aofthe first telephone lineisconnected zen of the United States, residing at New with the levers of the spring jacks b c on the York, in the county of New York and State different boards and from the spring jack of New York, have invented a certain new through the subscribers individual drop d to and useful-Improvement in Metallic Circuits ground. The other branch 6 of the first telefor Multiple-Switchboard Systems, (Case No. phone line is connected with the insulated 2,) of which the following is a full, clear, conframes of said spring jacks b c, and when no cise, and exact description, reference being plug is inserted, said branch cwiil be open at to had to the accompanying drawings, forming the switch board. a part of this specification. Referring now to Fig. 2, it will be seen that My invention relates to telephone exchange branch at is permanently connected with the systems in which metallic circuits are used telephone switch lever, and when the telein connection with multiple switch boards, phoneis hung upon the switch lever, as shown, I5 and consists in providing a ground connecthe circuit of, line a is closed through the tion for both branches of the metallic circuit bell and generator to ground. at the subscribers station, so that the ordi- Line 6 is shown connected with a contact nary calls may be made over one branch or point f, against which the switch lever rests limb of the circuit, while the other branch or when the telephone is hung thereon; hence 2o limb connected with the insulated frames of theline c is also grounded at the subscribers the different switches of the line may be used station as long as the switch rests upon point as a test wire. When the subscriber takes f. Calls may therefore be sent over branch his telephone from the switch, this ground win the usual manner between the subscriber connection is broken at the subscribers staand the central office. Line 6 being normally tion and the two branches or limbs are united open at the central oiiice and closed at the to form a metallic circuit which is completed subscribers station, it is evident that when a at the central office through a pair of loop test is made by connecting a telephone in cirplugs and cords, as hereinafter described. cuit with a battery with the insulated frame lily invention consists in placing the diiferof either of the switches 19 c, circuit will be 0 cut magnets of each of the clearing out drops closed through said wire (2 to ground at the in different strands of the cords, so that the subscribers station. The click resulting in resistance in the two sides or different limbs the telephone will indicate that the line is of the metallic circuit may be balanced. free.

My invention will be readily understood by V'Vhen the subscriber takes down his tele- 5 reference to the accompanying drawings in phone, the lever is separated from point f and which the ground contact of the bell and generator, Figure 1 is a diagram of two metallic cirand closed with the upper contact points, thus cuits connected with their switches respectclosing the local circuit in the ordinary way ively on two multiple switch boards, and the and uniting the two lines a e in a metallic 4e different magnets of the clearing out shutcircuit through the telephones. The metallic o ters included in different strands of the pairs circuit thus formed may be traced by line a of cords. Fig. 2 is a diagram illustrative of to the switch lever, thence to point g'thence the circuits at a subscribers station when the through line 9 to binding post 0 through the subscribers telephone is hung upon the secondary of the induction coil to post 0 then 5 switch lever. Fig. 3 is a sectional View showto line e. Thus when the telephone is on the 9 5 ing the loop plug in detail. Fig. shows the switch lever, the contact point f is closed to two magnets of the clearing out drop in consaid switch lever and the branch containing nection with their common armature. the bell and generator is closed to ground. Like parts are indicated by similar letters On removing the telephone, the lever is dis- 50 of reference throughout the different figures. connected from point f and the ground 'con- Ioo nection, and closed to point g, the local circuit being also closed at the same time.

The local circuit may be traced from the battery 1' to the switch lever, thence to contact 13, through the receiver to post m, through the primary of the induction coil to post no, thence to battery.

Referring now to the connections upon the switch board of branches at and e, it will be seen that when a plug is inserted as shown in switch I), branch 9 will be connected from the insulated frame of the spring jack to the insulated sleeve upon the plug and thence to a strand of the conducting cord; we will say strand 7a. Branch a being connected with the lever of the switch will be disconnected from the ground contact of the switch and closed to the tip of the plug and thence connection will be made with the other strand of the cord; we will say strand 1'. The connect-ion with the other line is made with the other plug of the pair and the second subscriber is summoned byloopingin the generator. \Vhen two lines are thus connected together and a test is made at any spring jack of either of the lines upon any of the boards, no circuit will be found since the wires are disconnected at the subscribers stations and connected together to form a single metallic circuit. There fore if a line wanted is busy when a test is made at one of the test pieces or rings, current will be sent through the telephone and hence no click will be heard. If, therefore, the operator when testing hears no click in the telephone, he will know that the line is in use.

Having thus described my invention I claim as new and desire to secure by Letters Patcutl. In a multiple system of telephone exchange, the combination with a spring jack switch on each of two or more boards, of a metallic circuit provided with a branch circuit to ground at the subscribers station, one of the branches of said circuit being normally connected through said spring jacks and an annunciator to ground, and the other branch being connected with the insulated frames or test pieces of said switches and normally open, and switching apparatus at the subscribers station, whereby said ground at the subscribers station may be taken off and the two branch es connected together through the subscribers telephone to form a metallic'circuit substantially as shown and described.

2. In combination with spring jacks one on each of two or more multiple switch boards, of a metallic circuit consisting of two branches, one branch being normally connected through the spring jack switches to ground, the other branch being connected to the insulated frames or test pieces of said switches and normally open, and switching apparatus at the subscribers station and at the central office, whereby said branches may be united to form a metallic circuit substantially as described.

3. In a multiple switch board exchange system the spring jacks of a telephone line, one on each board, said spring jacks being each provided with an insulated frame or test piece to which one branch of the metallic circuit is connected, the other branch being connected through said spring jack switches, testing apparatus at the central office and switching apparatus at the subscribers station for connecting said lines to ground or with each other in metallic circuit, whereby one branch of said circuit may be used as a test wire or united with the other branch in a metallic circuit substantially as described.

In witness whereof I hereunto subscribe my name this 6th day of November, A. D. 1886.

JOHN A. SEELY.

\Vitnesses:

II. I THAYER, A. L. SALT. 

